Spatial progressive scan converted interlace pictures provide reduced visibility of horizontal line structure in displayed images by doubling the number of lines displayed per field. Typically, the "extra" lines for display are obtained by some form of interpolation of the transmitted lines by means of an interlace-to-progressive scan converter. Such converters may tend to exhibit, in general, unsharp vertical transitions along horizontal structures and show only an insignificant reduction of interlace flicker. This is normally due to the use of vertical interpolation or a simple vertical average over two lines applied at horizontal structures. One result of that kind of "up-conversion" is very often that the original interlace pictures may look better than the up-converted ones for certain images being displayed. Generally speaking, conventional spatio-temporal up-conversion algorithms are effective only over a relatively limited range of velocities of moving objects. For greater velocities these algorithms may tend to produce an intolerable temporal lag making the contours of the moving objects rather unsharp. Many proposals exist which employ a combination of different optimized processing modes for moving or still picture parts in an attempt to overcome motion artifacts but the included motion detector problems have not been completely solved up to now.